I just got my 70-200 F2.8IS and would like to use a clear or UV filter on it to protect the front glass.

Questions. I was thinking of either the Hoya UV multi-coated or super multi-coated Pro-1 filter. Any strong recommendations of one over the other? From your experience will either of these reduce image quality (using a 20d)?

Get the best you can, if you are going to use them.
Any filter will potentially add image degradation, and add source for lens flare at each air/glass interface.

I use one depending on the situation, in normal shooting it is off the lens.
In a storm, bad weather, or where there may be spray of some kind I put one on so I can just wipe it off as needed with a cloth.

If you think your filters are high priced, try getting a 105mm :G
I got a UV and a polarizer for my 120-300 F2.8 and the pair set me back close to 600$cdn :?

The debate about whether or not to use a filter for protection comes up about once every month or so - there are strong feelings on both sides of the fence about whether or not you should use one. If you do decide, then get the best - if Hoya, use Super HMC - you don't need the PRO-1 since the only benefit over the Super HMC is that the pro-1 is a thinner mount (which comes into play in wide angles). For use on a 70-200 you wouldn't gain any benefit using the PRO-1 over the Super HMC - they both have the same multi coating.

The only other thing I'll add is I believe Hoya has come out with new digital line of filters in the last few months which supposedly have a different coating to cut down on issues more prevelent with digital cameras - I can't say whether they work or not or have a noticeable affect.